\begin{tikzpicture}
	\pgfmathsetmacro{\R}{2.5}
	\tkzDefPoints{0/0/B, \R/0/A}
	\tkzDefPoint(21:\R){D}
	\tkzDefPoint(42:\R){C}
	\tkzDrawSegments(B,A  B,D  B,C)
	\tkzLabelPoints[left](B)
	\tkzLabelPoints[right](A, C, D)
\end{tikzpicture}

